1. Field of the Invention
The present invention relates to an apparatus and method for measuring thermo-physical properties of a reservoir fluid.
2. Description of Related Art
The measurement of reservoir fluid properties is a key step in the planning and development of a potential oilfield. It is often desirable to perform such measurements frequently on a producing well to provide an indication of the performance and behavior of the production process. Examples of such measurements are pressure, volume, and temperature measurements, often referred to as “PVT” measurements, which are instrumental in predicting complicated thermo-physical behavior of reservoir fluids. One important use of PVT measurements is the construction of an equation of state describing the state of oil in the reservoir fluid. Other properties of interest that may be determined using PVT measurements include fluid viscosity, density, chemical composition, gas-oil-ratio, and the like. Once a PVT analysis is complete, the equation of state and other parameters can be input into reservoir modeling software to predict the behavior of the oilfield formation.
Conventional PVT measurements are performed using a cylinder containing the reservoir fluid. A piston disposed in the cylinder maintains the desired pressure on the fluid, while the heights of the liquid and gaseous phases are measured using, for example, a cathetometer.
Despite wide application, conventional PVT measurements suffer from several significant limitations. Firstly, a conventional PVT analysis typically requires up to a few weeks to complete. Furthermore, a substantial volume of reservoir fluid, often as much as 4 liters, must be maintained at pressures up to about 1400 kilograms/square centimeter (20,000 pounds/square inch) from the wellsite to the testing laboratory. Shipping and handling such a large sample at these high pressures is costly and poses considerable safety issues.
While there are ways of characterizing properties of reservoir fluid known in the art, considerable shortcomings remain.